Marker assisted breeding for the maize nutritional enhancement

Abstract

Combined with traditional selection techniques, marker assisted breeding aimed at the maize nutritional enhancement has been established at the Maize Research Institute Zemun Polje. Over the years, commercial maize inbred lines of standard quality have been converted to quality protein maize (QPM), as well as beta-carotene rich (BCR) maize, adapted to temperate regions. These newly developed lines were used for developing high-yielding maize hybrids with improved nutritional benefit adapted to temperate regions. Simple sequence repeats (SSR) were efficiently used for direct selection of target gene (foreground selection) and for fast recovery of recurrent parent's genome (background selection). As gene-specific markers in foreground selection, phi057 and umc1066 were used for QPM lines, while crtRB1-3TE marker was used for BCR lines. Background selection was performed with SSR markers evenly distributed throughout the genome. The recovery of the recipient genome in our best lines varied from 93% to 99% for QPM and from 90% to 99% for BCR. Biochemical evaluation of resulting improved hybrids showed increase of relevant nutritional parameters. Tryptophan content and tryptophan to protein ratio, an indicator of improved nutritional protein quality, were significantly higher (p<0.05) in QPM hybrids compared to standard maize. Also, tryptophan was above 0.075%, which corresponds to the QPM threshold value. Similarly, beta-carotene content in BCR hybrids was significantly higher (p<0.01) in comparison with the standard hybrids (increase up to 78.11%). Furthermore, starch and lipid contents were significantly higher (p<0.01) in improved hybrids. These results confirmed the success of the marker assisted conversion process, resulting in hybrids with improved nutritional value for use in feed industry